This invention relates to a check valve of a fuel tank for preventing fuel from flowing in the reverse direction from a fuel tank to an oil filler port in an oil filler pipe.
It is known that in a fuel tank of an automobile or the like, the moment the fuel tank becomes full during feeding, fuel suddenly flows in the reverse direction from the fuel tank to an oil filler port in an oil filler pipe. A check valve is a component which is provided at the end of the oil filler pipe opened to the fuel tank or in the oil filler pipe and put in the closing state except being pushed to open by fuel flowing from the oil filler pipe toward the fuel tank, and for example, cited is the valve in which a valve element having a turning shaft disposed on the valve seat side is energized from the fuel tank side toward an oil filler port by a torsion coil spring. U.S. Pat. No. 5,301,709 is taken as an example of the above type, and in addition, U.S. Pat. No. 5,285,816 and U.S. Pat. No. 5,355,910 have proposed a check valve in which a flat valve comprises two layers, a first soft flexible layer and a second layer of a rigid plastics material, and the hinge part is formed only by the former soft flexible layer.
To accomplish designated operation in the above mentioned structure, the check valve has to satisfy the mutually contradictory requirements for holding down the pressing force of the valve element to the valve seat to be always opened in feeding fuel and for the sealing performance between the closed valve element and the valve seat in fuel reversal. That is, in order to easily open the valve in oil feeding, the energizing force to the valve element has to be held down, and on the contrary, in order to secure the sealing performance in the valve closing state, it is desirable that the energizing force to the valve element is increased to press the valve element to the valve seat. Especially the sealing performance in the valve closing state is important for fuel slowly flowing in the reverse direction due to increase in pressure in the fuel tank after the fuel tank is made full by oil feeding.
U.S. Pat. No. 5,301,709 shows a check valve (corresponds to a check valve of the present invention) having a pair of semicircular valve discs with openings, in which a seal material press-contacting the valve element in the valve closing state is formed on the peripheral edge of the valve seat to mainly improve the sealing performance in the valve closing state. The check valve, however, has the problem that the structure is so complicated as to cost high and be inferior in assembling efficiency.
Accordingly, the inventors of the present invention have previously proposed one disc type valve plate improved in assembling efficiency and fitting efficiency, which is provided on the end of an oil filler pipe in a fuel tank in U.S. Pat. No, 5,327,933. On the basis of the above proposal, the present invention has examined the structure of a new check valve of such a type as to be installed in the interior of a pipe, which is not inferior in assembling efficiency and improved in sealing performance in the valve closing state.